Mods to Duane Gray's PD "at" program

[Bob Wilber]

I got bored and did some clean up on Duane Gray's public domain at program.
The changes are simple but extensive, so rather than me send out patches
anyone interested should send me mail and I'll send out the new shar
files.

What changed: I fixed up locking so that one user can't lock out everybody else
forever (did that one a while back) and I rationalized the error messages.

Bob Wilber  wilber at research.att.com